So many investigators have no fear of testifying about their work ... as investigators. But when they have to testify about technical matters, image analysis as an example, they recoil at the thought of having to explain a very complex task to a jury. Why?
Why should you fear testimony? Certainly some do fear public speaking in general. This is to be expected; much in the same way a child will fear his/her first trip into the batter's box. The ball does move rather fast. The bat's kinda heavy. Everyone's watching. How will he/she make it? The same way you will. Practice and planning.
Start with your warm-up. How do you arrange your work area when beginning a case? Work your way through your SOP. In the theatre of your mind, go step-by-step through the workflow. Can you repeat your own work? Was your work reviewed in your own lab or elsewhere? If so, why. If not, why not. What is it about your experience and training that makes you qualified to work this case? Then go from there.
Rehearse your answers. In this way, you hear yourself saying the answers and become comfortable with speaking these technical terms and phrases. You won't get tongue-tied saying "three dimensional colour deconvolution" if you say it out loud enough times. Same is true with other terms like de-multiplexing, photogrammetry, and pixel aspect ratio.
If you plan on referring to your notes during testimony, make sure that the print is large enough to read. Try double spacing and using a serif font that's at least 16 pt.
Practice and planning can make all of the difference in the world. It should be a regular part of your routine. With a little practice, you'll see court as an opportunity to shine ... not an event to be missed at all costs.